Sara Momenipour, PhD

Iran is a significant global iron producer, hosting over 200 iron oxide deposits (IODs). In 2023, the country produced approximately 78 Mt of iron ore. Iran boasts reserves of 4.2 Gt of iron oxide, account for approximately 1.7% of global reserves by 2024. Most of this production comes from Iron oxide-apatite (IOA) or Kiruna-type, Skarn, sedimentary and volcano-sedimentary (Fe ± Mn) banded iron ore (BIO), iron oxide copper-gold (IOCG), sideritic Fe-Mn (Cu-Zn-Pb-Ba) Irish-type, laterites, Fe-Mn veins, and placer deposits. The Dehbid district in the southern part of the SSZ is one of the most important iron oxide mining districts, hosting numerous Fe (±Mn) deposits and prospects in Late Triassic – Early Jurassic carbonate rocks and schists. The Dehbid mining district is situated within the Heneshk shear zone, associated with the Zagros Mountains' major oblique-slip thrust fault. Brittle deformation is also prevalent and is characterized by extensive faulting, and geological contacts exhibiting fault displacement. Although some researchers advocate for a vein geometry of iron mineralization in these deposits, detailed geological and structural studies indicate that a significant portion of the iron mineralization is stratiform to stratabound, hosted in Triassic-Jurassic silicified dolomites. However, in some deposits, tectonic activities and later magmatism have also led to the concentration of Fe-Mn ores in carbonate rocks along the later fault zones. The iron oxide mineralization occurs as lenticular orebodies, 100 to 700 meters in length and 2 to 10 meters in thickness, trending northwest-southeast with a dip of 40 to 50 degrees northeast. The mineralized dolomites and schists have been thrust over the metamorphosed volcanic-sedimentary sequences of the Late Triassic-Early Jurassic, by a northwestern-southeastern trending reverse fault, dipping towards the northeast. Detailed geochemical data represents that the Fe₂O₃ content of ore bodies varies widely from 30 to 91 wt% magnetite-hematite ores. The average content of MnO in the iron ores is high (5 wt%, up to 57%) but P₂O₅ is typically low (0.15 wt%). MgO content in mineralized rocks is high (av. 1.6 wt%, up to 7%), and the values of CaO are significant (av. 8%, up to 46%). The concentration of trace elements in the studied ores are very low, such as Cr (av. 70 ppm), Co (av. 25 ppm), Ni (av. 42 ppm), Ag (av. 2 ppm), Mo (av. 28 ppm and Pb (av. 18 ppm). Zn (34.3 ppm), but Cu (av. 519 ppm, up to 4350 ppm) and Zn (av. 194 ppm, up to 3270 ppm) show higher concentrations. Au also represents very low concentration, up to 50 ppb in the orebodies. Textural relationships between ore and gangue minerals indicate that these ores are sedimentary banded iron deposits. This is supported by LA-ICP MS data of magnetite in stratiform iron ores, showing low concentration of Al, Ti, V, Cr, Co, Ni, Cu, and other trace elements, plus high values of Mn, Fe/V and Fe/Ti ratios.